1. Field of the Invention
This invention relates to systems for creating images of a scene. More specifically, this invention relates to systems operative to generate a scene image spanning a wide field-of-regard.
While the present invention is described herein with reference to a particular embodiment, it is understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional embodiments within the scope thereof.
2. Description of the Related Art
Infrared imaging systems are used in a variety of military and commercial applications to provide either an operator or a guidance system with a view of a scene. Such imaging systems are typically characterized as having a "field-of-regard", which refers to the angular breadth of the resultant scene image. One benefit accruing from a wide field-of-regard is that a viewer of the wide-field image may observe individual objects therein within the context of a larger scene. However, increases in the field-of-regard generally come at the expense of decreases in image resolution within conventional imaging systems.
Various methods have been utilized in an attempt to avoid the necessity of compromising image resolution to achieve a wide field-of-regard. For example, in a particular optical approach the imaging system is designed to incorporate a pair of optical lenses. One of the lenses encompasses a wide field of view, while the other covers a relatively narrow field of view. The lenses are then mechanically moved in and out of the optical train of the imaging system to alternately provide a wide field-of-regard or improved resolution. One disadvantage of this approach is that the rate at which an operator may switch between the fields of view of the two lenses is limited by the response of the servo system used to alternately interpose the lenses within the optical train. In addition, it is often difficult to capture a moving object within the field of view of the high resolution lens even though the location of the object may be readily apparent within the wider field of view.
In a second approach, an imaging sensor (typically having a relatively narrow field of view) is mounted on a gimbal scan mechanism. The gimbal is rotated to direct the field of view of the sensor to various regions within the field-of-regard, with frames of image data being produced by the sensor at a known rate (e.g. 60 Hz). Although individual regions throughout the entire field-of-regard may be viewed in isolation using this method, a composite image of the entire field-of-regard is not produced. It is also generally difficult to maintain a moving object within the sensor field of view (by rotation or scanning of the gimbal) without "smearing" the resultant image. Moreover, complex processing methods are required to create images across consecutive frames of image data.
In a third approach, image data from a number of separate sensors are used to generate a real-time image of an entire field-of-regard. The field of view of a first sensor is arranged to overlap slightly the field of view of a different sensor in order to prevent seams from appearing in the composite image. However, complex and expensive image processing hardware is typically required to implement this multi-sensor scheme. In addition, multi-sensor systems offer only minimal improvement in signal-to-noise ratio relative to single sensor systems.
It follows that a need exists in the art for a single sensor, high resolution imaging system having a wide field-of-regard.